Recent increase in the environmental consciousness leads strong desire for the development of a detergent with low environmental load. A detergent having higher concentration of a cleaning component than that of conventional detergent, or a concentrated detergent, appears as being very effective for decreasing its own size to reduce an amount of resin used for container, a transportation cost, a waste after use, and the like, resulting in reduction of loads on the environments.
Such a surfactant-rich liquid detergent composition however has problems of difficulty in stably blending a builder component in addition to storage stability of the composition itself. For example, polyacrylic acid polymers are known to have good properties of dispersing mud and preventing re-deposition of the mud. These polymers are generally difficult to be stably blended in an aqueous surfactant system. In some cases, an aqueous surfactant system blended with a polyacrylic acid polymer causes clouding, separation such as phase separation, and/or precipitation of a base material in the solid form in a solution during storage.
In addition, when a concentration of the surfactant that is a cleaning ingredient of a liquid detergent is increased, the liquid detergent tends to cause thickening and/or gelation. To control thickening and/or gelation, there is a method of adding a large amount of organic solvent to such a liquid detergent to decrease a water content. The method however has a dissolution problem by formation of liquid crystals due to dilution with water in washing.
JP-A 2008-7705, JP-A 2008-7706 and JP-A 2008-7707 describe concentrated liquid detergent compositions containing a specific nonionic surfactant. These compositions still have a problem of solubility in water. There is no suggestion about stable blending of a polymer.
JP-A 10-60476 and JP-A 10-60496 describe liquid detergents containing a polymer produced by graft polymerization of a polyether compound such as polyethylene glycol as the main chain with a monoethylenic monomer component mainly composed of acrylic acid or methacrylic acid. These prior patents disclose concentrated surfactant systems, but do not consider the dissolution problem during dilution.
JP-A 2004-155937 describes a polymer having two segments for dispersing a nonionic surfactant and a water-insoluble solid matter, where the nonionic surfactant is salted-out by addition of a large amount of water-soluble inorganic salt. The patent discloses a concentrated and solid-dispersed liquid detergent containing a polymer of a polyethylene glycol acrylate and acrylic acid as the polymer having two segments. The patent relates to a technique of stably dispersing droplets of the nonionic surfactant accompanied with the water-insoluble solid matter in an aqueous phase prepared as having a high salt concentration in the liquid detergent of multi-phase, not in a uniform system.
JP-A 2005-187742 discloses a surfactant composition containing a nonionic surfactant prepared by addition of EO and PO, a polymer, and a water-soluble inorganic salt dispersed in the composition. U.S. Pat. No. 4,814,102 and U.S. Pat. No. 4,897,215 disclose detergents containing a copolymer prepared from a monomer having a carboxyl group and a monomer having a polyglycol group. WO-A98/023712 discloses a surfactant composition containing a nonionic surfactant, prepared by addition of EO and PO, and a polymer.